During drilling with a hammer grab using an attachment in the form of a casing oscillator/casing rotator, two units that are per se independent work together in the preparation of a pile. The base machine in the form of a cable excavator comprises a hammer grab for excavating a hole. A casing oscillator/casing rotator likewise fastened to the cable excavator serves the clamping of the casing that is to be introduced into the ground by uniform rotational movements synchronously to the excavation. The required energy for the casing oscillator is typically provided by the base machine.
The operator of the cable excavator/drilling rig or of the casing oscillator/casing rotator, for example, sets the energy flow to the casing oscillator/casing rotator via a regulator. The disadvantage of this method is that the energy flow is so-to-say static and can only be changed sporadically. It can occur here, in dependence on the workstep or on the work cycle, that the casing oscillator is provided either with too much or too little energy for the respective work, whereby not only the total energy consumption is unnecessarily increased, but likewise delays in the work routine have to be accepted.
A solution is therefore sought that is able to overcome the disadvantages explained above.
This object is achieved by a method of power management during pile foundation having a base machine for excavating a borehole and an attachment installed at the base machine for a simultaneous introduction of a casing into the ground, wherein an energy supply for the attachment is at least partially provided by the base machine. Starting from the method of the category, it is proposed in accordance with the invention that a control of the base machine dynamically regulates the energy flow from the base machine to the attachment. The base machine can, for example, be a cable excavator that is equipped with a corresponding hammer grab drill for excavating a borehole or with a drilling rig such as a Kelly drill. The attachment is, for example, a casing oscillator or a casing rotator for introducing a casing into the ground.
In accordance with the invention, the control of the base machine should dynamically regulate the distribution of the energy between the attachment and the base machine in order thereby to optimize the capacity and effectiveness of the two machines. It is primarily a question of hydraulic or pneumatic energy that is provided to the attachment by the base machine. The method is, however, not restricted to a specific type of energy and could equally be used for the energy management of electrical energy.
It is sensible if the regulation of the energy flow takes place while taking account of the current power requirement of the base machine and/or of the attachment. The process routine is meaningfully known to the control or the control has knowledge of future worksteps of the base machine or of the attachment. In cyclic processes, this knowledge can also be learnt from past cycles. If, for instance, one of the two consumers is always stretched to its limits energetically in the same part cycle and if simultaneously the other consumer does not require the total energy, a dynamic adaptation can be learnt. A dynamic regulation of the energy flow can thereby take place on the basis of this information on subsequent worksteps. Specifically, the total energy expenditure for the preparation of the pile is composed of the power requirement of the base machine for the excavation of the borehole and the power requirement of the attachment for introducing the casing. The respective cyclic worksteps performed on the units are characterized by a variable power requirement. It is accordingly sensible to supply the attachment with less energy during the carrying out of worksteps with less energy expenditure to be able to instead utilize the surplus energy in the base machine. If instead a process with a high energy requirement takes place in the attachment and if the base machine requires comparatively little power, it is sensible to maximize the energy flow to the attachment. Individual worksteps can thereby be directly carried out faster, which can optimize the total process time. The total energy requirement during the pile foundation process can also hereby be optimized since the unnecessary provision of surplus energy to the base machine or to the attachment is prevented or at least reduced.
It is conceivable for the dynamic regulation to limit the energy flow to the attachment or to stop it completely under certain circumstances. A limitation can take place stepwise, for example. A continuous limitation is, however, also conceivable to enable an adjustment of the energy flow that is as fine as possible.
As claimed, the control of the energy flow takes place by a control of the base machine. It is, however, likewise conceivable to outsource the process performance to an external control in part, for example to the control of the attachment. There is meaningfully a communication interface between the base machine and the attachment to be able to exchange information relevant to the process for the dynamic regulation of the energy flow between the machines.
There is likewise the possibility of exchanging a demand for a power reduction or a power increase between the machines over the communication interface. It is, for example, conceivable that the base machine or the control of the base machine requests the attachment to reduce its energy consumption over the communication interface to thereby ensure a higher power proportion for the base machine. Conversely, the attachment could also request an increase of the energy flow to the attachment from the base machine over the communication interface.
A corresponding request for a power reduction to the attachment can also include an instruction on and a specification of worksteps of the attachment to be carried out. It is conceivable in this context that the base machine specifies worksteps to be carried out to the attachment or recommends one or more worksteps. Such a recommendation is meaningfully based on the base machine's own power requirement. If it requires a comparatively large amount of power, the specification or recommendation includes energy-saving worksteps; conversely, the carrying out of high-energy worksteps is recommended/specified if surplus energy is currently available on the part of the base machine.
The process time of individual worksteps can be directly influenced or controlled by means of the dynamic regulation of the energy flow. This relates to worksteps both of the attachment and of the base machine. The rotational movement of the attachment can, for example, be specifically accelerated by the provision of additional energy. Conversely, a power reduction produces a delay or a slowing down of the respective worksteps.
It is of particular importance for the pile foundation and in particular for an optimum energy expenditure during the pile foundation that the casing process is synchronized with the simultaneous excavation of the borehole. If, for example, the excavation of the casing takes place in advance, there is the risk of a crashing of the casing, which can cause material damage and costs. If, however, the casing is too far in advance, the jacket friction on the inner side becomes too large, which can cause higher energy costs. The progress of both processes should accordingly be kept approximately the same or the casing depth should be slightly in advance of the excavation depth with a constant interval.
This relationship makes a monitoring of the different between the depth of the earth excavation and the casing depth sensible, with the determined difference being taken into account in a further step in the dynamic regulation of the energy flow. The depth difference is in particular maintained above and/or below a lower or upper limit value by the active influencing of the power distribution.
It is particularly advantageous if the energy flow to the attachment is restricted if the casing depth is larger than the excavation depth by at least a limit amount. Conversely, it can be sensible to increase or even to maximize the energy flow to the attachment if the excavation depth is larger than the current casing depth by at least a limit amount. Such a relationship between the depth difference and the power distribution can be particularly advantageously mapped by a cost function, with this determining the average power proportion to be output to the attachment in dependence on the depth difference, for example.
As was already indicated above, the work processes of the attachment and/or of the base machine can be divided into cyclically occurring individual steps that also differ from one another with respect to the power requirement. It is particularly advantageous for the optimization of the power management to take account of the performance or future performance of the individual steps during a complete work cycle in the dynamic regulation of the energy flow. It is sensible here that the energy flow to the base machine is dynamically set on the basis of the average power proportion while further taking account of the cyclic excavation process of the base machine. This can optionally take place by multiplication of the average power value by a weighting parameter that characterizes the current individual step of a complete work cycle. It is specifically possible that such a weighting parameter is smaller during the digging and lifting of the excavation tool of the base machine than during the lowering and emptying of the excavation tool. The selection of the suitable weighting now provides that a smaller power proportion (for example, a weighting factor less than 1) is provided to the attachment during the digging and lifting of the base machine since the digging and lifting process of the base machine is comparatively energy-intensive. Conversely, the power requirement during the lowering and emptying of the excavation tool of the base machine is much lower; surplus energy can be provided to the attachment by the selection of a higher weighting factor, for example of approximately 1.
An optimum efficiency of the power transfer results on a specific position of the two oscillating cylinders due to the geometry of the design of a typical casing oscillator. The efficiency decreases on large deviations in both directions. The effective oscillation angle at the front of the casing reduces in particular with very large casing depths due to twisting of the casing. Against this background, it is sensible likewise to set this oscillating angle dynamically during the operation or as the casing depths increase. It has proved sensible here for the attachment to set the oscillation angle dynamically while taking account of the current power consumption of the attachment and/or in dependence on the casing depth or the excavation depth. The work process or the effectiveness of the casing oscillator can hereby be ideally set since an optimum, maximum oscillation angle can be set while taking account of the aforesaid values.
The soil strength at the current work location is of further significance. This factor can also be taken into account for the optimum setting of the attachment or of the base machine. A further pipe section can in particular be installed to improve the contact pressure with a poor driving of the casing oscillator. It is also conceivable that in such a case the casing oscillator specifically requests more energy for the casing procedure from the base machine over the communication interface. The casing oscillator can set the current advance speed, for example while taking account of the depth change of the casing over time.
In addition to the method in accordance with the invention, the present invention also relates to a system comprising a base machine, in particular a cable excavator or drilling rig, and at least one attachment, optionally a casing oscillator or a casing rotator. The attachment and the base machine comprise at least one control for carrying out the method in accordance with the invention. The control of the method is in particular taken over by a control of the base machine. The system is accordingly characterized by the same advantages and properties such as have already been explained in detail above with reference to the method in accordance with the invention. A repetitive description is dispensed with for this reason.